This invention relates to communications networks, generally, and more particularly to a method of communication within such communications networks and apparatuses for practicing the inventive method.
The World Wide Web (xe2x80x9cWebxe2x80x9d) is essentially a distributed depository of data files stored on Web servers connected by a global communications network known as the Internet. Users of the Web may request transmission of files to their own computers, i.e., Web clients, for viewing, storing or printing. Each Web server stores files identified by a universal resource locator (URL) comprising an electronic address. Each URL is a physical reference in that each URL points to a particular server and identifies the location of a single file at that server. Many of the files stored on Web servers are documents written in a standard programming language known as hypertext mark-up language (HTML). The standard HTML syntax of Web pages and the standard HTTP communications protocol supported by the Web guarantee that a Web client and Web browser can communicate with any Web server. The JAVA programming language and JAVA applets allow for platform independent application programs which can be executed by any Web client.
HTML files are translated for viewing, printing or storing by a Web browser computer program running on the Web clients. The Web browser also communicates with Web servers. Using HTML, an author of such a Web page (a file written in HTML) can designate a specific word, phrase or image in the Web page as a hyperlink. Each hyperlink may be associated with a URL of another Web file. A user""s selection of a hyperlink is an initiation of a request for the file located at the electronic address identified by the URL with which the hyperlink is associated. Since each traditional hyperlink is associated with a single URL, each hyperlink is associated with a single file having a particular location on a particular server.
A request for transmission of a file originates at the Web client and is submitted to a Web server by the Web browser software running on the Web client. In a typical arrangement, the request is then forwarded to a proxy computer interconnecting the client computer and the server computer. Upon a user""s selection of a hyperlink, the client""s Web browser issues a hypertext transfer protocol (HTTP) request to the Web server identified by the URL associated with the hyperlink. The request is intercepted by a proxy which then relays the request over the Internet to the identified Web server. The Web server responds by transmitting the requested file to the proxy, assuming that the requested file resides on the Web server at the electronic address identified in the URL. The proxy then relays the requested file to the Web client.
If the Web server does not have the requested file at the electronic address identified in the URL, the Web server transmits an error message to the Web client and the client does not receive the requested file. In such a case, the hyperlink associated with the incorrect URL is referred to as a xe2x80x9cbroken linkxe2x80x9d. This frequently occurs, for example, when a Web page is written such that a hyperlink is established to a file having a particular electronic address on a server and the file is subsequently deleted from or moved relative to the server. If the Web page is not updated to revise the URL associated with the hyperlink to reflect the file""s current electronic address, a broken link results.
Accordingly, it is an object of the present invention to enhance access to a file and reduce the problem of broken links by providing a method for satisfying a request for information which identifies a file independently of its location on a particular server.
It is another object of the present invention to provide such a method which is compatible with existing communication protocol, and Web browsers.
It is yet another object of the present invention to provide apparatuses for carrying out the inventive method.
These and other objects are realized by the provision of a system for transmitting files over a communications network in which links, such as hyperlinks, to files comprise a new construct herein termed an indirect link. An indirect link is a logical link identifying a file to be retrieved, not by its electronic address or URL, but by a logical reference. The logical reference may identify the server on which the file exists, but does not identify the file""s complete electronic address, i.e., an identification of a particular server and the file""s location on that server. Rather, the server or a proxy computer uses a look up table which relates the logical reference to an actual current electronic address at the server containing that file. The use of indirect links helps minimize the occurrence of broken links, since a file can be moved from the location at which it existed when a hyperlink to it was created, yet still be retrieved from the server. If a regular hyperlink of the prior art had been used, once the file had been moved from the electronic address (e.g., URL) to which the hyperlink pointed, the file could not be retrieved through that hyperlink.